1. Field of the Invention
The present invention relates to a defect inspection apparatus inspecting a defect on a substrate, a sensitivity calibration method for the same, a substrate for defect detection sensitivity calibration that is used for calibrating detection sensitivity of a defect detection apparatus, and a manufacturing method thereof.
2. Description of the Related Art
In manufacturing a semiconductor device, it is necessary to inspect the occurrence of a defect such as a so-called cone defect. The cone defect is formed when a semiconductor substrate is etched due to a foreign substance adhering on the substrate or is etched due to a foreign substance during processes of forming various kinds of patterns. In accordance with the recent progress of the miniaturization of a system LSI circuit, in order to detect more microscopic defects, the wavelength of an illumination light used in a defect inspection apparatus targeted at a semiconductor device under the design rule of, for example, a 65 nm to 90 nm size is becoming still shorter. This has given rise to a problem that it becomes difficult to determine the proper optimization of sensitivity.
Conventionally, there has been proposed a reference substrate for defect detection sensitivity calibration. In the reference substrate for defect detection sensitivity, programmed foreign substance portions that are highly discriminatable are regularly formed (see a patent document 1). This substrate is used for discriminating (judging) the quality of the detection sensitivity of a defect inspection apparatus for foreign substance inspection or of an appearance inspection apparatus.
[Patent Document 1] Japanese Patent Application Laid-open No. Hei 7-120404
In the reference substrate for defect detection sensitivity calibration as proposed in the patent document 1, programmed defective portions are provided as a regular pattern, and the heights of the programmed defective portions are adjusted to a constant value of 50 nm to 200 nm. On the other hand, in a chip area on an actual semiconductor substrate, complicated semiconductor elements and wiring patterns different in size are densely formed. Therefore, even when defect detection using the reference substrate for defect detection sensitivity calibration as proposed in the patent document 1 detects a large number of microscopic defects, it is difficult to appropriately cope with a case where an unexpected change occurs in the defect inspection apparatus. Concretely, in actual semiconductor processes, when a light source (for example, a laser light source, a lamp, or the like) is replaced in an illumination part of the defect inspection apparatus, the number of detected microscopic defects changes to a relatively great extent. However, there is a problem that the defect inspection using the reference substrate for defect detection sensitivity calibration as described in the patent document 1 cannot fully ensure defect detection sensitivity.